[NEW DELHI] A small group of Himalayan glaciers grew in size when the earth became hotter 9,000 years ago, new research shows.

Summer Rupper, professor of geology at Brigham Young University in the United States, reports in the September issue of Quaternary Research that a small group of Himalayan glaciers grew by several kilometres 9,000 years ago — during an 'inter-glacial' period when central Asia grew hotter by six degrees Celsius.

Her findings are based on a model that predicts both glacier mass and energy balance at its surface under varying regional climatic factors such as temperature, humidity, cloudiness and rainfall, and wind.

Rupper reports that shifting weather patterns at the time brought more clouds and winds to the area, making it cooler and helping ice formation. Her team is now extrapolating the findings to a new project to predict future water changes in the area — now under threat as glaciers melt because of global warming.

The report helps us better understand how a rise in temperature affects the height at which snow accumulates, Anil Kulkarni, coordinator of the snow and glacier project at the Space Applications Centre, Ahmedabad, told SciDev.Net.

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However, the paradox of glaciers increasing in size — and not melting — during warmer conditions occurred under very different conditions.

During the last four inter-glacial periods, including the period addressed in Rupper's research, that occurred in the past 350,000 years, carbon dioxide concentrations remained below 300 parts per million (ppm). Present carbon dioxide levels have exceeded 380 ppm because of global warming, Kulkarni told a South Asian media workshop on climate change last month (27 August).

Satellite data from 1962 to 2004 indicates that more than 1,000 Himalayan glaciers have retreated by around 16 per cent, Kulkarni says.

The glaciers are retreating at varying speeds. Some are melting faster, such as the Parbati glacier at a rate of 50 metres per year and Gangotri at 28 metres; while others like the Pindari glacier are retreating more slowly, at five metres per year.

The Himalayan glaciers are breaking into pieces and many are not forming new ice, "A large number of glaciers have no [ice] accumulation," Kulkarni says.

Scientists at the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, Nepal, also report large-scale melting in Himalayas of 10—60 metres each year, while the Imja glacier south of Mount Everest is retreating by 74 metres each year.